LANDING STRING RETAINER SYSTEM

Abstract

A retainer system, device and method are provided for retaining a severed pipe string such as a landing string suspended from a rig of a floating vessel or platform during a failure of a primary or secondary heave compensation system and prevent the severed pipe string from flying over the rig floor. The retainer system includes a retainer device including a housing mounted to a platform or vessel, the housing defining a through bore for receiving a pipe string suspended from the platform or vessel. A safety sleeve extends through the housing. A stop arrangement is mountable on the pipe string, to permit engagement between the safety sleeve and the stop arrangement in order to limit relative movement between the housing and the pipe string in order to retain a severed pipe string in an emergency situation.

Claims

1. A retainer system comprising: a retainer device comprising a housing mountable to a platform or vessel, the housing defining a through bore for receiving a pipe string; a safety sleeve extending through the housing; a stop arrangement mountable on the pipe string; wherein engagement between the safety sleeve and the stop arrangement limits relative movement between the housing and the pipe string.

2. The retainer system as in claim 1, wherein the retainer system is connectable to one or more heave compensation systems connected with the platform or vessel.

3. The retainer system as in claim 1, wherein the retainer system is installed above or below a rig floor of a platform or vessel.

4. The retainer system as in claim 1, wherein the retainer device is mountable to the platform or vessel so that the through bore of the housing is aligned with a through bore of a rotary table installed on a rig floor of a platform or vessel.

5. The retainer system as in claim 1, wherein the through bore of the housing permits the pipe string to be deployed freely therethrough and for the safety sleeve to be mounted therein.

6-12. (canceled)

13. The retainer system as in claim 1, wherein the safety sleeve is releasably fastened to the housing

14. The retainer system as in claim 1, wherein the safety sleeve is or comprises an insert adapted to be positioned within a corresponding pocket of the housing.

15. (canceled)

16. The retainer system as in claim 1, comprising a dynamic sealing arrangement to be positioned between the safety sleeve and the pipe string.

17. The retainer system as in claim 1, wherein the safety sleeve comprises a cylindrical tubular body that fits around the pipe string.

18-19. (canceled)

20. The retainer system as in claim 1, wherein the safety sleeve is secured within the housing by an annular packer urged against the safety sleeve.

21. The retainer system as in claim 1, wherein the safety sleeve defines the shape of an annular ring positioned within the housing in close proximity with the pipe string so that the annular ring is capable of engaging the stop arrangement of the pipe string.

22. (canceled)

23. The retainer system as in claim 1, wherein the safety sleeve comprises an impact absorption section aligned to engage the stop arrangement of the pipe string.

24-25. (canceled)

26. The retainer system as in claim 12, wherein the impact absorption section comprises a dampening mechanism.

27. The retainer system as in claim 1, wherein the safety sleeve slidably fits around the pipe string, allowing a clearance between the pipe string and the safety sleeve, the clearance between the pipe string and the safety sleeve being adjustable.

28. (canceled)

29. The retainer system as in claim 1, comprising a seal for sealing between the safety sleeve and the housing.

30-31. (canceled)

32. The retainer system as in claim 1, wherein the stop arrangement comprises a structure mountable on an outer surface of the pipe string.

33. The retainer system as in claim 1, wherein the stop arrangement comprises a continuous annular structure.

34-36. (canceled)

37. The retainer system as in claim 1, wherein the stop arrangement comprises a dampening portion and/or a dampening mechanism.

38. A retainer device for a pipe string, the retainer device comprising: a housing mountable to a platform or vessel, the housing defining a through bore for receiving a pipe string suspended from the platform or vessel; a safety sleeve extending within the housing; wherein the safety sleeve is adapted to engage a stop arrangement associated with the pipe string to limit the relative movement between the housing and the pipe string during operations.

39. A pipe string comprising a stop arrangement associated with the pipe string, wherein the stop arrangement is adapted to engage a safety sleeve of a retainer device to arrest the movement of the pipe string during operations.

40-84. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0112] These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0113] FIG. 1 is a simplified diagrammatic illustration of an upper region of a retainer system according to an embodiment of the present invention, wherein a pipe string is shown suspended from a floating platform;

[0114] FIG. 2 is an enlarged, longitudinal cross-sectional view of region A of the retainer system of FIG. 1 showing a pipe string extending through a rotary table, and a retainer device in a normal operating condition;

[0115] FIG. 3 is an enlarged, longitudinal cross-sectional view of region A of FIG. 1, in an emergency condition, wherein a severed pipe string is stopped by the engagement of a stop arrangement associated with the pipe string with a safety sleeve of the retainer device, according to an embodiment of the present invention;

[0116] FIG. 4 is an enlarged, longitudinal, cross-sectional view of region A of FIG. 1 showing a different embodiment of the present invention retainer system in a normal operating condition;

[0117] FIG. 5 is an enlarged, longitudinal cross-sectional view of region A of FIG. 1 of the same embodiment as the one shown in FIG. 4 but in an emergency situation;

[0118] FIG. 6 is a diagrammatic illustration of a retainer system comprising a constant tension bail system, according to an embodiment of the present invention;

[0119] FIG. 7A is an enlarged, longitudinal cross-sectional view of a constant tension bail shown connected to low and high fluid accumulators in a locked position, according to an embodiment of the present invention;

[0120] FIG. 7B is a longitudinal cross-sectional view of a constant tension bail shown in a mid-stroke position, according to an embodiment of the present invention;

[0121] FIG. 7C is a longitudinal cross-sectional view of a constant tension bail shown in a full stroke position, according to an embodiment of the present invention;

[0122] FIG. 8 shows a constant tension bail, according to a different embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0123] During subsea drilling, workover or production operations, a pipe string such as a drill string, or a landing string may connect a subsea well to a rig or platform such as a floating platform or vessel. The pipe string may be deployed within a larger pipe string, as is common, for instance, to deploy landing strings used in workover operations within a larger marine riser. The marine riser may also connect the subsea well to the rig. Typically, a first end of the pipe string may be suspended from a derrick positioned on the rig floor while a second end may be connected to the subsea wellhead. Although the invention will now be described in reference to a landing string system and a floating platform, it should be understood that the present invention retainer system may be employed equally with any other pipe string or rig.

[0124] Referring now to FIG. 1, an upper region of a retainer system, generally identified by numeral 2 according to an embodiment of the present invention is provided, wherein a pipe string 1 is shown suspended from a platform or rig 4 floating on a body of water 27. The pipe string 1 is a landing string suspended from a heave compensated top drive 3 mounted on a rig. It should be understood that the invention works equally well for pipe string systems deployed from any type of platforms or vessels including but not limited to mobile offshore drilling units employed in conjunction with subsea wells, or Jack-up drilling rigs employed in conjunction with surface wells on a steel jacket, or stationary drilling units employed in development fields.

[0125] The landing string 1 is suspended from the top drive 3 via cables or rigid rods 9, clamps 13, 11 and pipe connector 29. Pipe connector 29 may have fluid connections 26 for supplying fluids to the landing string and/or bleeding down any fluids trapped in the landing string during decommissioning.

[0126] The landing string 1 is deployed through a rotary table 5, a retainer device 6 and a workover riser 8. The landing string 1 is connected at its lower end to a wellhead of a subsea well (not shown). Tensioned cables 15 suspend the riser 8 from a riser connector 16 to a riser heave compensator arrangement 7.

[0127] A umbilical 18 is shown placed next to the landing string 1 for providing fluid, power, data communication, control communication or a combination thereof to the landing string 1 and or operations in an associated well or well equipment.

[0128] The retainer device 6 as shown in FIG. 1 comprises a retrofitted flow diverter housing. An outlet 14 is mounted to the housing 6, however, it should be understood that the outlet may form an integral part of the housing 6, however, it should be understood that the retainer device may comprise a specifically made housing.

[0129] A flow diverter is typically positioned below a rig floor, between riser and the rotary. The flow diverter may be used to safely vent unbalanced wellbore pressure which may otherwise escape from the top of the riser, thereby posing a hazard to personnel and equipment.

[0130] Referring now to FIG. 2, an enlarged, longitudinal cross-sectional view of region A of FIG. 1 is provided, showing the flow diverter housing 6 mounted via a cylindrical connector member 17 to a rig structure 19 below the rotary table 5. The flow diverter housing 6 defines a through bore 6a along a central longitudinal axis. The flow diverter housing is positioned immediately below the rotary table so that the through bore 5a of the rotary table 5 may be aligned with the through bore 6a of the flow diverter housing 6.

[0131] A safety sleeve 10 having a cylindrical tubular body 10a and a rim at an upper end 10b is suspended, via the rim end 10b, from the rotary table 5. The safety sleeve 10 extends through the through bore 5a of the rotary table 5, through the cylindrical connector member 17 and into the through bore 6a of the flow diverter housing 6. The flow diverter housing 6 comprises a piston or ram element 20 which may be activated to urge an annular packer element 21 against the safety sleeve 10 to seal off the area around the safety sleeve 10.

[0132] The annular packer element 21 may be made of any suitable packer material for obtaining effective sealing around the landing string 10. A dynamic seal (not shown) may be employed between the safety sleeve 10 and the landing string 1 to seal off the clearance between the safety sleeve 10 and the landing string 1 as the landing string 1 moves relatively to the housing during operations.

[0133] The safety sleeve 10 may be secured to the rotary table 5 by connectors (not shown) such as threaded lugs and nuts. Other connectors may be used to connect the safety sleeve to the diverter housing 6. However, it should be understood that the safety sleeve 10 may alternatively be securely positioned within the flow diverter housing 6 simply by the action of the piston 20 urging the annular packer element 21 against the safety sleeve 10. Stated otherwise, the safety sleeve 10 may be sufficiently secured within the housing simply by the action of the piston 20 urging the packer element 21 against the safety sleeve 10 rendering the need to secure the safety sleeve 10 via connectors redundant.

[0134] The landing string 1 comprises a stop arrangement 12. The stop arrangement 12 may be securely mounted at the external surface of the landing string 1. During normal operations, neither the safety sleeve 10 nor the stop arrangement 12 may interfere with the free movement of the landing string 1.

[0135] However, in the event of an emergency situation, the safety sleeve 10 may engage the stop arrangement 12 of the landing string 1 to stop the upward movement of the landing string 1 as it is shown in FIG. 3. Thus, the retainer system may limit the relative movement between the landing string 1 and the housing 6 to prevent the severed landing string 1 from ejecting out of the housing.

[0136] Referring now to FIGS. 4 and 5, another embodiment of the retainer system is provided that employs a diverter housing 106 similar to those used in connection with insert packer diverters. Features of the embodiment of FIGS. 4 and 5 which are similar to features shown in the embodiment of FIGS. 2 and 3 employ like numerals, incremented by 100. The embodiment of FIG. 4 may be implemented by retrofitting existing insert packer diverters, however it may also be implemented by constructing a custom made housing 106.

[0137] The housing 106 comprises a first outer member 122 and a second inner member 123 assembled together via a plurality of fasteners 124. First outer member 123 is mounted to a rig structure 119 via a connector member 128. First outer member 123 defines an outlet 114 which is in fluid communication with a corresponding port 130 of the second inner member 122. A marine riser 108 is mounted to a lower end 122a of the second inner member 122.

[0138] A safety sleeve 110 comprises an insert placed inside a corresponding pocket 125 of the first inner member 122 of the housing 106. The insert and pocket as shown in this embodiment may be of a bayonet design allowing the insert to be readily dropped or inserted inside the pocket 125 at a first time and locked in place by turning it at a second time. Such a design is advantageous as it may facilitate installation and maintenance both for retrofit as well as custom made systems. However, other means of securing the insert may be employed such as for example using a threaded insert fitting within a corresponding female threaded pocket. Other means of securely mounting the safety sleeve 110 may be used.

[0139] Further, it should be appreciated by the skilled person that the shape, size and material of construction of the safety sleeve 110 may vary, provided that the safety sleeve 110 is designed to not interfere with the relative movement or proper functioning of the landing string 1 during normal operations. At the same time, the safety sleeve 110 should provide adequate resistance to the impact upon engagement of the stop arrangement 112 of the landing string 1, in an emergency condition.

[0140] A dynamic seal (not shown) may be employed to seal off the clearance between the safety sleeve 110 and the landing string 101. Also, a static seal (not shown) may be employed to seal off the area between the safety sleeve 110 and the first inner member 22 of the housing 106. Conventional well-known dynamic or static seals may be employed.

[0141] The landing string 101 has a stop arrangement 112. The stop arrangement may be mounted at the external surface of the landing string 101 using one or more well-known fasteners or may form an integral part of a landing string section. The safety sleeve 110 may be positioned within the pocket 125 allowing sufficient clearance between the safety sleeve 110 and the landing string 101 to permit free vertical movement of the landing string 1, in normal operating conditions as shown in FIG. 4.

[0142] In an emergency situation, if the landing string 101 is severed because of excessive tension overcoming the tensile failure limit of the landing string 101, the upper part of the landing string 101 may be prevented to eject out of the housing 106 by virtue of the safety sleeve 110 engaging the stop arrangement 112 of the landing string 1 as shown in FIG. 5.

[0143] Referring now to FIG. 6, another embodiment of the present invention retainer system is provided, comprising an emergency string tensioning system 231 also referred to herein as a constant tension bail system 231. However, it should be understood that the retainer system may be used in combination with any other heave compensation system and may not be limited to the constant tension bail system 231 as shown in FIG. 6. It should be noted that the embodiment of the retainer system of FIG. 6 shares many features in common with the embodiment of FIG. 1, and for easy reference any common features are denoted using the same numerals as in the FIG. 1. As shown in FIG. 6, the emergency string tension system 231 comprises two identical tension modules 232 employed to suspend a landing string 1 from a top drive 3. Each tension module is referred to hereinafter also as a constant tension bail or bail. It should be understood that the emergency string tensioning system may comprise one or more constant tension bails 232 without departing from the scope of the present invention. Each bail 232 comprises an outer cylindrical housing 235 and end connectors 232a and 232b attached at each end of the housing 235. End connectors 232a are connected via cables 233 to a clamp 11 which is, in turn, mounted to the top drive 3. End connectors 232b are connected via cables 234 to a pipe clamp 13 which is, in turn, attached to the landing string 1.

[0144] Under normal operating conditions, the constant tension bail system 231, as shown in FIG. 6, operates like ordinary bails, i.e. without extension. However, when the tension exerted on the system exceeds a predetermined level then the constant tension bail system 231 may extend in order to provide supplementary tension regulation and prevent the severing or breaking of the landing string 1.

[0145] Referring now to FIG. 7A the structure of an embodiment of the constant tension bails 232 will be described in more detail. The constant tension bail comprises a cylindrical housing 235 which defines a cylindrical cavity 239 therein. The bail 232 further comprises a telescopic member generally designated with numeral 255 which in a normal operating condition as shown in FIG. 7A is locked to the outer cylindrical housing 235 using a lock and release module or mechanism generally designated with numeral 243. The telescopic member 255 comprises an end connector 232b having a cable 234 connected thereto at one end for connecting the bail 232 to a pipe string. The telescopic member 255 further comprises a piston rod 249 which connects the telescopic member to a first piston 238.

[0146] The cylindrical housing 235 further defines two ports, a first port 250 also referred to hereinafter as a low pressure port, and a second port 251 also referred to hereinafter as a high pressure port. The second port 251 is disposed generally proximate a lower end 239a of the cylindrical cavity 239. The first port 250 is disposed proximate a median position between lower and upper ends 239a and 239b of the cylindrical cavity 239.

[0147] Alternatively, if in the event that tension from for example a primary or secondary heave compensator reaches below a predetermined level due to malfunction or failure, the constant tension bail system will retract in order to maintain a predetermined level of tension on the landing string.

[0148] A second piston 240 having an inner cylinder 236 integrally mounted thereon is disposed within the cavity 239 of the cylindrical housing 235. Inner cylinder 236 extends from the second piston 240 to the upper end 239b of the cylindrical cavity 239. A first chamber 241 is defined within cylinder 236 between first and second pistons 238 and 240. Seals 253 provide sealing between the inner cylinder 236 and the cylindrical housing 235.

[0149] Inner cylinder has a port 257 so that the first port 250 may be in fluid communication with first chamber 241 via an annulus 260 defined between the inner cylinder 236 and the cylindrical housing 235. First piston 238, also referred to as a floating piston, is slidably movable within the inner cylinder 236 between a first upper position proximate to the end 239b of the cylindrical cavity 239 to a second position defined by the end 236a of inner cylinder 236.

[0150] The floating piston 238 is connected to the telescopic member 255 via the piston rod 249. The piston rod 249 extends from the floating piston 238, through a through bore 252 defined centrally within second piston 240, to the telescopic member 255.

[0151] The second piston 240 is also referred to herein as a slow moving piston. The second piston 240 may slidably move within the cavity 239 defined within the outer cylindrical housing 235 from a first position starting at the end of the inner cylinder 236a to a second position defined by the end 239a of the cylindrical cavity 239.

[0152] The second piston 240 comprises a central through bore 252 through which the piston rod 249 may freely move relative to the second piston 240. A second fluid chamber 242 is defined within the cavity 239 between the second piston 240 and the end 239a of the cylindrical cavity 239. Seals 244 are disposed on the internal surface of the through bore of piston 240 and seals 245 are disposed on the external surface of piston 240 to ensure pressure and fluid isolation between the first and second chambers 241 and 242.

[0153] Chamber 241 contains a first fluid maintained at a first pressure by fluid supplied via port 250 and a related conduit 246 from a first fluid accumulator 247. Chamber 242 contains a second fluid maintained at a second pressure by fluid supplied via port 251 and a related line 254 from a second high fluid accumulator 248.

[0154] Each constant tension bail 232 may further comprise a lock and release mechanism 243 that locks the telescopic member 255 to the outer cylindrical housing 235 so long as the force exerted on the telescopic member 255 is below a predetermined level.

[0155] When the force exerted on the telescopic member 255 reaches or exceeds the predetermined level, then the lock mechanism 243 is unlocked to release the telescopic member 255 to extend in order to reduce the tensile force exerted on the pipe string. Thus, so long as the lock mechanism 243 is engaged, each constant tension bail 232 may not extend. However, while the lock mechanism 243 is engaged, each constant tension bail 243 may retract when the force exerted on the telescopic member 255 reaches below a predetermined level.

[0156] The lock mechanism may be a manual lock and release mechanism, a remotely actuated lock and release mechanism, or a combination thereof.

[0157] If the lock mechanism 243 is manual, the bails 232 may be locked manually upon installation, and may be manually released by use of riding belt operations in the derrick or they may be manually accessed from a work platform to release them. For re-locking the bails 232, another manual rigging belt or work platform operation would have to be performed.

[0158] If a remotely actuated bail lock and release mechanism is used, a cable may be used to connect the bails to a control panel for the activation mechanism Release or re-engagement of the lock, as may be needed, may be performed remotely via the control panel. The lock mechanism may, according to one embodiment, comprise one or more shear pins (not shown) that hold the telescopic member securely attached to the housing 235.

[0159] Under normal operating conditions the shear pin may be designed to break under a mechanical overload that reaches or exceeds a certain predetermined level. The shear pin may be designed to shear once the mechanical overload reaches or exceeds a safe tensile failure limit for the landing string.

[0160] During use, the floating piston 238 may provide a first constant tension to the landing string 1, controlled by a set point mechanism, acting in support of the normal rig heave compensation system, by providing a finer regulation of the landing string tension than the rig heave compensation system can provide. The floating piston may also act as a pure back-up for constant string tension, in case the rig heave compensation system is not functioning as intended.

[0161] If a serious malfunction occurs with the rig heave compensation system, the floating piston 238 will bottom out on top of the second piston 240 as shown in FIG. 7B. In that event, if the bail 232 is forced to extend further, as it may occur in the event of a rig heave-compensator lock-up, the second piston 240 would act as an emergency break.

[0162] As a result, the tension force that the bail 232 provides will increase, but preferably not to a point where the landing string 1 may be severed. This is achieved by the higher pressure hydraulic fluid of chamber 242, supplied by the external hydraulic accumulator 248 via port 251. The tension force level maintained may be pre-set via a regulation mechanism. The regulation mechanism may be hydraulic pressure supplied by accumulator 248, or any other suitable technical device.

[0163] When the second piston 240 reaches the end stop position as shown in FIG. 7C, control may be lost, and the landing string 1 may be severed if, the tensile force exerted on the landing string 1 exceeds the tensile failure limit of the landing string 1. If this happens, the constant tension bail 231 may act as a shock absorber, breaking the upward movement of the landing string 1 as it tries to eject out from the well bore. In addition, the constant tension bail may start to close, going back to its original normal operational stroke range. In this manner, the constant tension bail system may prevent the severed landing string from falling on the deck of the rig floor.

[0164] According to an embodiment of the invention accumulators 247 and 248 may provide same pressure to both chambers 241 and 242. However, employing a low and a high fluid accumulators is preferred as this way the bails 231 may provide a two-step tension release mechanism for releasing the tension exerted on the landing string 1 in an emergency situation.

[0165] Referring now to FIG. 8 another embodiment of a constant tension bail 331 is provided. For ease of reference similar features between this embodiment and the embodiment of FIGS. 7A to 7C are referred to with similar numerals augmented by 100. Thus, bail 331 comprises a housing 332 defined by a cylinder 335 that defines a cylindrical cavity 339 therein. Within the cylindrical cavity 339 there are disposed two pistons, a first piston 338, also referred to as a floating piston and a second piston 340 also referred to as a slow moving piston. The first piston 338 is connected to a telescopic member generally designated with numeral 355. Telescopic member 355 comprises an end connector 332b and a piston rod 349. In a normal operating condition, as shown in FIG. 8, the telescopic member 355 is locked to the cylinder 335 via locking mechanism 343.

[0166] Piston 340 comprises a central through bore 352 with seals 344 that allow the piston rod 344 to freely move relatively to the piston 340 while preserving pressure isolation between chambers 341 and 342.

[0167] Piston 340 also comprises seals 345 disposed on the periphery of the piston rod 349 to seal off the clearance between the piston rod 349 and the interior wall of the cylindrical cavity 339 as piston 349 slidably moves within cylinder 335.

[0168] The pistons 338 and 340 define two chambers 341, and 342 within the cylindrical cavity 339. A first chamber 341 is defined between the floating piston 338 and the second piston 340. A second chamber 342 is defined between the second piston 340 and an end 339a of the cavity 339.

[0169] The first chamber 341 contains a first fluid maintained at a first pressure via a fluid supplied via a first port 350 from a first accumulator (not shown).

[0170] The second chamber 342 contains a second fluid maintained at a second pressure via a fluid supplied via a second port 351 from a second accumulator (not shown) in a similar manner as described earlier in relation to the embodiment of FIG. 7A.

[0171] Seals 345 disposed on the periphery of piston 349 to preserve pressure isolation for chamber 341 as piston 338 slides within cylinder 335.

[0172] Piston rod 349 extends longitudinally along a central axis of the housing 332 from piston 338 through piston 340 through an aperture 354 of the housing and a through bore 355 defined within the locking mechanism to the telescopic member 355. An end connector 332b is mounted to the telescopic member 355 for ready connection to a pipe string.

[0173] It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto, without departing from the scope of the present invention.